In the disclosure of the present invention reference is mostly made to the treatment of diabetes by delivery of insulin, however, this is only a an exemplary use of the present invention.
Conventional delivery devices for delivery of liquid drugs by means of subcutaneous injection typically have been provided as devices such as pen-shaped devices having a cylindrical form-factor. The cylindrical form-factor approach has mainly been chosen due to the particular use of cylindrical drug-filled cartridges. While the cylindrical form-factor generally enables design of slim devices, this form-factor typically has short-comings as regards device length and available surface area for presenting information to the user, e.g. by means of a display.
To overcome these problems, delivery devices having form-factors other than the pen-shaped form-factor have been proposed. Examples of injection devices having both the cylindrical form-factor as well as devices having a non-cylindrical form factor are disclosed in WO 98/10814.
Generally, from a users viewpoint there is a wish that the delivery device is as slim and short as possible in order to provide for a compact device which may be easily carried about, i.e. in a shirt-pocket or the like. At the same time, there is a wish that modern injection devices offer an increasingly variety of features. Such features may include a large display for presenting the size of the set dose, a large maximum dosing amount available for each single administration, automatic expelling of set doses, the prevention of setting a dose exceeding the drug amount remaining in the device, etc.
In a recent publication, WO 2011/045611 discloses a spring driven injector having a dose setting arrangement to select a dose volume and a drive mechanism which in some forms include a preloaded spring having stored energy sufficient to expel the entire useable contents of a cartridge over a succession of doses. In accordance with the teachings of WO 2011/045611 the proposed injection devices presents drawbacks having regard to building length. In addition, the proposed window arrangement for indicating set doses provides a far from user friendly design as it includes a window that rotates relative to the housing as the dose is being dialled. Furthermore, potentially unsafe situations may occur if a mechanical defect should occur within the device causing an uncontrolled expelling of the entire contents of the cartridge.
WO 2007/017053 discloses a syringe device that comprises a dose limiting mechanism to prevent ejection of a dose exceeding a set dose and a safety mechanism that prevents ejection of a dose exceeding the set dose in case the dose limiting mechanism should fail.
Having regard to the above discussion, it is a first object of the present invention to provide a medical injection device that is safer in use compared to prior art injection devices.
It is a further object of the present invention to provide an injection device that includes a secondary safety mechanism that enables more flexibility in the design than in prior art devices.
It is a further object of the present invention to provide an injection device that is more compact than prior art devices.
It is a still further object of the present invention to provide an injection device that is superior in user friendliness compared to prior art devices.